1. Field of the Invention
The instant invention relates to that field of devices consisting of articles of manufacture known as dowel pin drilling guides. Specifically, the instant invention is an adjustable dowel pin hole drilling guide.
2. Background Information
The prior art known to applicant discloses that dowel pin drilling guides are relatively well known within the art. These drilling guides have ranged from the simple, as embodied in U.S. Pat. No. 2,798,520 issued to J. M. Maskulka on Jul. 9, 1957, to the relatively complex, as embodied in U.S. Pat. No. 4,752,162 issued E. F. Groh on Jul. 21, 1988.
In Maskulka, the primary object of the invention was to create a drill guide which would allow a wood worker to assemble wooden frames without resorting to the traditional mortising of the joints. This was accomplished by creating a device which had an essentially "L" shaped body, the body having two tubular openings, the bore of the tubular openings passing completely through one "leg" of the "L" shaped body. The user of the device would simply lay the wood frame which was to be drilled so that it was cradled by the body, and the tubular openings aligned with the areas of the wood frame which were to be drilled.
This approach worked reasonably well for drilling the flattened ends of wood frames. However, as proposed by Maskulka, it was less than simple to use when drilling the ends of wood frames which were cut on an angle. To drill guide holes on an angled end of a wood frame, the user was forced to carefully measure and locate a center line on both pieces of wood. If the center line was off even slightly on either piece, the two pieces would fit together unevenly, thereby negating the device's intended benefit. While this requirement of a carefully located center line applied even to the flat ended wood frame, Applicant believes it was less likely to cause serious errors as a piece of wood frame work which is composed entirely of 90 degree angles as it is much easier hold in place and measure than is one having more or less steep angles.
A further, and even more serious drawback to the Maskulka device was that it was practically useless when trying to place dowel pins into a wood frame which incorporated compound angles. Applicant has learned that when assembling certain wooden articles, it is necessary to utilize compound angles. For example, if one wished to construct a wooden cone using wood strips, it is necessary to include a compound angle along each side to be joined to another wood strip. The device described in the Maskulka patent cannot be used along such compound angles without a great deal of careful measurement and shimming prior to clamping the device to the wood strip.
Finally, the device described in Maskulka provides for the drilling of guide holes at a pre-determined distance from one another. It is impossible to drill, for example, two holes approximately 3 centimeters apart and also drill another set of holes approximately 5 centimeters apart. The distance between the holes is a function of the distance between the two tubes, and no variability is therefore possible.
Other prior art has attempted to deal with the problem of variability of distance between holes. For example, in Groh, the drilling of holes at varying distances is accomplished by the inclusion of two bodies nearly identical to that disclosed in Maskulka. However, in Groh, these two bodies are connected to one another via a rod passing through each body that permits the distance between the two bodies to be varied.
Unfortunately, Groh suffers from the same shortcoming as does Maskulka; it cannot easily be used when drilling guide holes into material having compound angles. Furthermore, when used to drill holes at the end of a plank of wood (or other material), Groh is unwieldy, and works best when its inventive feature (the rod permitting adjustability) is removed. When used in this fashion, the Groh device is simply another version of the Maskulka device, and fails to perform certain tasks in the same fashion as does the Maskulka device.